Corrugated plate type heat exchanger



D. M. COX

June 24, 1969 CORRUGATED PLATE TYPE HEAT EXCHANGER sheet Filed July 19, 1967 l@ Weg;

June 24, 1969 D. M. COX

CORRUGATED PLATE Tw HEAT EXCHANGER Sheet 2 of 2 Filed July 19. 1967 ATTORNEY United States Patent O CORRUGATED PLATE TYPE HEAT EXCHANGER Dean M. Cox, Whtestown, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed lIuly 19, 1967, Ser. No. 654,606 Int. Cl. F28f 3/ 04 U.S. Cl. 165-166 9 Claims ABSTRACT OF THE DISCLOSURE My invention is directed to improved heat exchangers of the fixed or recuperator type. While my invention is capable of various uses, it is particularly suited to pro vision of a recuperator for use in gas turbines and other systems in which a large heat transfer area is required to transfer heat from a gas at relatively low pressure to another gas `at relatively high pressure.

In a typical regenerative gas turbine system air is compressed by a compressor, heated in a heat exchanger, further heated by combustion of fuel, expanded in one or more turbines, and then iiows through the heat exchanger to transfer heat from the turbine exhaust gas to the compressed air. Both fixed heat exchangers, which I call recuperators, and rotary heat exchangers, which I call regenerators, have been employed for this purpose. The regenerators present very considerable problems of sealing, and ordinarily the recuperators are both bulky and diicult to make leakproof. One reason for this difficulty lies in the provision of high pressure passages formed from light weight sheet metal. Thin metal sections are employed for high heat transfer in a device of reasonable volume.

According to my invention, a heat exchanger is provided in which there are no high pressure passages in the ordinary sense, the high pressure path extending between `a number of wafers each defining a low pressure path through the heat exchanger, the high pressure gas being conned by a casing which encloses the heat exchange pack made up by the wafers.

The principal objects of my invention are to provide a compact and leak-free heat exchanger particularly adapted for use with gases at substantially different pressures, to provide a heat exchanger of small weight and volume for its heat transfer capacity, and, more speciti cally, to provide a heat exchanger in which the structures defining the low pressure passages are wafer-like in configuration and are formed of corrugated sheets such that the corrugations engage to preserve the separation of the sheets of the wafer and also to dene passages between the wafers for the other fluid.

The nature of the invention will be more clearly apparent from the succeeding detailed description of a heat exchanger which is the preferred embodiment of my invention and of the preferred embodiment of a process for manufacturing such a heat exchanger.

FIGURE 1 is an axonometric view, with parts cut away, of a heat exchanger of a cross-counterllow type.

FIGURE 1A is a fragmentary sectional view taken on its plane indicated by the line 1A-1A in FIGURE 1.

FIGURE 2 is a partial cross section of the same on a ICC plane indicated by the line 2 2 in FIGURE 1.

FIGURE 3 is a view of a corrugated sheet.

FIGURE 4 is a view of the same after folding and seam welding to form a wafer.

FIGURE 5 is an axonometric view of a stack or pack of wafers.

FIGURE 6 is a partial view of the same after brazing the end of the pack.

FIGURE 7 is a fragmentary cross-sectional view of the same to an enlarged scale as indicated by the line 7-7 in FIGURE 6.

FIGURE 8 is a view similar to FIGURE 7 after opening the ends of the wafers.

IFIGURE 9 is a partial end view of the pack as indicated by the line 9-9 in FIGURE 8.

FIGURE 10 is a fragmentary sectional view of the same taken on the plane indicated by the line 10-10 in FIGUR-E 9.

Referring iirst to FIGURES 1, 2, 'and 3, the heat exchanger comprises a pressure containing casing 13` in the general form of a rectangular tube 14 having end flanges 16 fixed to the ends of the tube. The tube includes an inlet side wall 17 having an inlet at 18 for high pressure gas and an outlet side Wall 19 opposite to side 17 dening a high pressure gas outlet 20, and includes two intermediate walls 22. One end flange 16 defines a rectangular inlet 23 and the other defines a similar outlet at the other end of the casing. Each end flange is of L section including a radially extending portion and an axially extending portion 25 which fits within the iiared end 26 of the tubular casing section 14. These parts` are brazed or otherwise bonded and sealed together.

The interior of the casing is filled yby a heat exchange pack 30. This heat exchange pack is made up of a stack of wafers 31, each wafer being a folded corrugated sheet to be described, having parallel walls 32. The walls of the wafers are parallel to the casing sides 22 and thus the wafers present their ends to the end flanges 16 and their edges to the sides 17 and 19 of the casing. The wafers have walls with corrugations as indicated at 34 in FIG- URES l, 3, and 4 which extend generally from end to end of the wafer but are preferably inclined -about 10 degrees to the endwise direction of the wafer. The corrugations on opposite Walls of a particular wafer are inclined oppositely to the axial direction so that the corrugations cross and engage each other where they cross. Each wafer has a folded edge 35 and a sealed (preferably seam welded) edge 36.

As will be more clearly apparent from FIGURES 3 and 4 each wafer preferably is made from a rectangular sheet 38 having ends 39 and sides 40 and which is provided with corrugations over substantially the entire surface, the corrugations extending at about a ten degree angle to the sides 4t). Preferably the margin of the sheet adjacent the sides and ends and a strip 41 through the center between the sides of the sheet are not corrugated.

The sheet is made into a wafer by folding the sheet along the central uncorrugated line 41 so that the two sides 40 meet as shown in FIGURE 4. After the folding, the two edges 40 are seam welded together and the ends 39 are closed by seam welding so that the wafer becomes temporarily a sealed capsule. When the sheet is folded, the corrugations on the opposite walls of the wafer are inclined to each other by about twenty degrees. Thus, they cross over at numerous points to abut each other and hold the walls of the wafer apart. Also, when the wafers are stacked to form a pack 42 as illustrated in FIGURE 5, the corrugations of adjacent wafers cross so that the peaks of the corrugations contact each other. The wafers 31 are stacked to provide a suicient size heat exchange pack 42 to fill the rectangular casing 13. Each wall of the wafer may be considered to be a corrugated plate, and the wafer is thus a set or pair of platos.

The seamed ends of the pack are then filled with braze metal at each end as indicated at 43 in FIGURES 6 and 7. This material covers the ends 39 of the wafers and also fills the space between the wafers to the plane 44 indicated in FIGURE 7 to hold the wafers together. The braze metal does not enter the wafers because these are closed at the fold and at the seamwelded side and ends.

The next step in making the heat exchange pack is to machine away the ends of the pack as shown in FIG- URES 8 and 9 to a plane face 45 back of the end seam so that the ends of the wafers are opened. However, the machining does not remove the braze metal remaining at 46 between the ends of adjacent wafers. This braze metal not only holds the matrix pack assembled, but it also blocks the ends of the passages between adjacent wafers as indicated at 46 in the FIGURES 8 to 10.

The structure of the heat exchange pack should be clear from the foregoing description of the assembly and of the process of manufacture. The lower p-ressure gas can flow into the wafers through openings 48 at one end of the pack 30 and out the similar openings at the other end. The high pressure gas can corne into the entrance 18 and flow out the entrance 20, flowing both across and lengthwise of the matrix pack between adjacent wafers 31. The high pressure gas is confined by the casing 13. The end iianges 16 of the casing are brazed or otherwise sealingly assembled to the matrix pack either at the same time that the braze metal 43 is applied, or later. The outer casing 13 may be wrapped around the flanges 25 and welded or brazed to the anges to complete the fluid-tight casing. Alternatively, the flanges 16 may be initially provided on the casing portion 14 and the heat exchange pack thereafter slipped into the casing and sealed at the ends to the wall of the casing by any appropriate means to prevent leakage of the higher pressure gas around the exterior of the heat exchange pack at the ends of the heat exchanger.

Ducts to conduct the hot and cold gases to and from the heat exchanger may be of any suitable configuration and attached by any suitable conventional means (not illustrated). As will be apparent, the relatively inclined corrugations of the heat exchange wafers provide a means whereby each wall has an array of points at which it abuts the adjacent wall and also provides a very substantial gas passage between it and the adjacent wall, whether this be a hot gas or a cold gas passage. Also, the relatively inclined corrugations promote turbulence and good heat conduction from the gas to the thin sheet metal wall, or vice versa. Because of the type of structure described, the walls between the hot low pressure gas and the cold high pressure gas may be quite thin, thus promoting compactness, light weight, and efficiency of the heat exchanger.

It may be noted that the drawings are not intended to show the structure to scale since the walls may be very thin as a practical matter. In a particular embodiment it is considered desirable to have the corrugations 34 on the sheet 38 and on the wafer formed from it to be approximately 0.043 inch from peak to peak with the depth of corrugations approximately 0.0143 inch. The sheet is of suitable high temperature and oxidationresistant metal such as stainless steel, approximately 0.003 inch thick in this embodiment.

The process described above provides for a very easy and economical manufacture of such a heat exchanger ack. p Obviously, the water can be made from two sheets each corresponding to half of sheet 38, the wafers being seam welded together around the entire margin.

Attention is called to my divisional application Ser. No. 770,921 for Heat Exchanger Manufacture filed Oct. 28, 1968.

The detailed description of the preferred embodiment of the invention for the purpose of explaining the principles thereof is not to be considered as limiting `or restricting the invention, since many modifications may be made by the exercise of skill in the art within the scope of the invention.

I claim:

1. A heat exchanger comprising, in combination,

a pressure-containing casing having ends and sides, having lan inlet and an outlet for one fiuid at the ends `of the casing, and having an inlet and an outlet for lanother fluid at higher pressure in lopposite sides of the casing,

a heat exchange pack mounted in the casing defining separate flow paths for the fiuids between the respective inlets and outlets,

`the heat exchange pack being an assembly of a plural number of healt exchange wafers,

each `wafer having two panallel walls seal'ingly joined at the edge-s and at least partially spaced at the ends of the wafer Iso as to define la passage from end Ito end of the wafer for `the said fone uid,

the walls having corrugations inclined differently to the direc-tion from end to end of the wafer, with the `corrugations of the two walls abutting at points where the peaks of the corrugations cross each other, to prevent collapse of the Wafer under external pressure,

a plural number of said wafers being s-tacked together in abutment w'ith Itheir edges directed toward the sides of :the casing which Provide the inlet `and outlet `for the other fluid, `the abutting wall-s of Iadjacent wafers having their corrugations relatively inclined so `that a conduit for lthe said other fluid is defined between adjacent wafers,

and wall means at the ends of the 4wafers blocking the said conduits and providing a seal between the wafers and the casing to prevent communication between the flow paths for -the two fluids.

2. A heat exchanger ias defined in claim 1 in lwhich corrugations in adjacent walls are oppos'itely inclined.

3. A heat exchanger as defined in claim 1 in which the walls are less than 0.005 inch thick.

4. A heat exchanger -as defined in claim 1 in which the depth of the corrugations 'is `about one lthird of the width of the corrugations.

S. A heat exchanger as defined in claim 1 in which the `said wall means includes `braze metal between the `wafers *blocking the said conduits.

6. A heat exchange structure comprising a plural number of heat exchange plates in stacked relation with each plate except the plates lat vthe top and bottom of the stack engaging two adjacent said plates and the top and bottom plates abutting an adjacent plate, ythe plates being of gener-ally rectangular form with ttwo sides and two ends and being stacked with :the Isides of `the plates at the sides of the `stack and Ithe ends of `the plates att ythe ends of the stack, the plates having corrugations covering substantially the entire surface of each platte defining suI stantially parallel ridges -On each lface of each plate, the ridges of alternate plates extending :in one common direction land the ridges of the plates interleaved between said altern-ate plates extending in a second common direction at an tangle to the first common direction so that the ridges of each plate engage the ridges of adjacent plates in ya two-dimensional array of points to preserve a spacing lbetween adjacent plates over the major portion of the surface of said plates, the plates of Ithe stack ybeing divided into sets with each set consisting of two adjacent plates, the plates of each set being joined |together along the sides to `define a iiuid passage through the set from end `to end of the stack, and the sets being jo'ined together :across the ends to define fiuid passages from side lto side of the 'stack between Vthe sets.

7. A heat exchange structure as defined in claim 6 in which the said plates `are all substantially identical and alternate plates are inverted.

8. A heat exchange structure as defined 'in `claim 6 in which the Walls are less than 0.005 ,inch lthick.

9. A heat exchange Istructure as defined in claim 6 in combination with a casing enclosing `the said structure defining inleits to and outlets Ifrom 'the passages through lthe sets and the passages fbetween the sets.

References Cited UNITED STATES PATENTS 3,183,963 5/1965 Mondt 165-166 XR 10 3,216,495 11/1965 Johnson 165--166 6 3,311,166 3/1967 Southam 165-166 3,341,925 9/1967 Gersftung 29-157.3

FOREIGN PATENTS 588,426 12/1959 Canada. 896,171 5/1962 Great Britain.

FRED C. MATTERN, JR., Primary Examiner'.

MANUEL ANTONAKAS, Assistant Examiner. 

